1. Field of the Invention
The present invention is directed to a ventilated air cooled cutting system having the ability to generate a thin cut in a material without overheating, and specifically, to a saw blade having a thin kerf with an integral cooling system to prevent overheating.
2. Description of the Prior Art
Within the wood processing industry, it has always been desirable to cut wood with the thinnest possible kerf, the kerf being the width of a cut made by a cutting tool. This is due to the fact that a larger kerf destroys more product while producing more waste as sawdust, while a thinner kerf produces a higher yield with less waste. A thinner saw blade is required in order to produce a thinner kerf. While thin kerfs of about 0.080 are produced by some band saw blades, band saws have a much slower cutting speed, making them less efficient.
Although it has been desirable to design a circular saw blade as thin as possible for a particular application, problems with designs have arisen physically limiting the ability minimize blade thickness. One of these problems is the generation of heat produced by the cutting action of circular saw blades as well as the torsional forces produced during the cutting operation. Of course, there are several variables that contribute to the generation of heat and production of torsional forces. Included among these variable are feed rates, species of wood being cut and condition of the cutting equipment. Nevertheless, when critical amounts of heat and torsion are produced, the saw blade can fail.
Typically, as blades are made thinner to reduce the kerf, they are less able to withstand torsion than thicker blades. In addition, the thinner blades have less mass and unlike thicker blades which can act more like a heat sink, having a higher heat capacity and more heat transfer capabilities, thinner blades have a tendency to become hotter faster. This tendency, coupled with the higher torsional forces, results in an undesirable shortening of the blade life.
Various solutions have been attempted to solve these problems. One proposed solution is set forth in U.S. Pat. No. 213,439 to Miller dated Mar. 18, 1879. This solution sets forth a blade having ventilating holes. While such a blade design can improve the transfer of heat, assuming the cooling holes are not clogged with sawdust, the design does not address the problem of torsion. Similar solutions are set forth in U.S. Pat. No. 88,949 to Emerson dated Apr. 13, 1869; U.S. Pat. No. 212,813 to Miller dated Mar. 4, 1879; U.S. Pat. No. 1,083,645 to Wettstein dated Jan. 6, 1914; U.S. Pat. No. 3,872,763 to Kayahara dated Mar. 25, 1975; and U.S. Pat. No. 4,776,251 to Carter dated Oct. 11, 1988. While these patents set forth apertures having varying geometries and arranged in various patterns to provide cooling for blades, they do not address the problems related to torsion associated with blades as they become thinner.
A second approach to improving saw blade operation is to reduce vibration by drilling slots in the blades. An added advantage to these slots is the ability to dissipate heat. This approach is set forth in U.S. Pat. No. 2,563,559 to Sneva dated Aug. 7, 1951; U.S. Pat. No. 3,107,706 to Heinemann dated Aug. 12, 1960; U.S. Pat. No. 3,730,038 to Farb dated May 1, 1973; U.S. Pat. No. 4232,580 to Stewart dated Nov. 11, 1980; and U.S. Pat. No. 4,240,315 to Tuomaala dated Dec. 23 1980. However, this approach may allow for use of a thinner blade due to reduced vibration and improved heat dissipation, it does not address the problem of shortened blade life associated with torsional effects.
What is lacking in the art is a blade that produces a thinner kerf, while providing sufficient cooling to prevent heat buildup in the blade, yet has sufficient strength to withstand torsion during cutting, so that blade life is not shortened.
The present invention is a cutting system comprising an air cooled cutting system that includes a circular saw blade that produces a thinner kerf, while having improved cooling capabilities, yet has sufficient strength and stiffness so that torsional effects of cutting do not adversely affect the life of the saw blade. The saw blade of the present invention preferably is formed from plate stock and has a blade cutting portion and a hub cooling and strengthening portion.
The blade cutting portion has a preselected diameter and a first thickness. These thicknesses can vary, but can be thinner than those currently utilized in the art. The blade cutting portion is a disk having an outer periphery. A plurality of blade teeth are formed in the outer periphery of the disk to provide a cutting surface. The teeth can assume a variety of forms depending upon the type of cut required and the type of material that is being cut. Blade teeth technology is well known in the art. The blade cutting portion may optionally include slots or strobes as described in the prior art to alter the natural vibration frequency of the blade.
The hub cooling and strengthening portion has an outer diameter smaller than the outer diameter of the blade cutting portion and having a second thickness greater than the first thickness of the blade cutting portion. Thus, the blade undergoes a cross-sectional change at the hub. This increased thickness has the effect of acting as a heat sink for the blade. As heat is generated in the blade cutting portion, the heat is transferred by conduction to the larger mass of the hub portion. The thicker hub portion also provides the additional advantage of being a strengthening member for the saw blade. Thus, the stiffer cross-section provided by the thicker hub assists in reducing the overall torsional effects to which the blade is subjected. The hub cooling and strengthening portion includes inner diameter defining a bore through which passes a motor-driven shaft that is used to provide the rotational motion for the blade during cutting operations. Because heat will be transferred by conduction to the hub portion, it is necessary to provide additional cooling to the hub beyond that which occurs as a result of natural circulation of air across hub surfaces. This additional cooling is provided by a plurality of cooling apertures extending through the second thickness of the hub in a substantially axial direction. These apertures are positioned on a diameter located intermediate the hub portion inner diameter and the hub portion outer diameter.
The cutting system of the present invention may include radially oriented slots which extend inwardly from the outer periphery of the blade and terminate within the blade cutting portion. These strobes or slots are within the art to modify the vibrational frequency of the blade. These slots typically are cut in a radial position and extend between the outer periphery of the blade cutting portion and the outer diameter of the blade cutting portion.
If additional cooling is required for the blade portion, the diameter of the hub portion can be adjusted to increase the heat capacity of the hub portion, thereby allowing more heat to be conducted away from the blade portion to the hub portion. Additional cooling to transfer heat away from the hub portion can be achieved by providing additional cooling apertures in the hub portion positioned between the hub portion inner diameter and the hub portion outer diameter.
An advantage of the present invention is that a blade having a thinner kerf can be made, without adversely affecting the life of the blade. Another direct advantage is the ability to saw a workpiece while reducing the amount of waste, thereby increasing the yield.
Another advantage of the present invention is that a blade having a thinner cutting portion can be produced without adversely affecting the ability of the blade to withstand the torsional effects of the sawing operations.
Still another advantage of the present invention is that the improved design permits the thin blade to be cooled efficiently by use of a thick hub as a heat sink for conductive heat transfer, while the hub is cooled by convection cooling. This cooling helps to extend the blade life by preventing deterioration from overheating.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.